This invention relates to systems for variably controlling internal combustion engine intake and exhaust valves. More specifically, it relates to engine valve systems of the type in which hydraulic pressure of a pressurized fluid is used through action of solenoid valves to control the engine valves motion.
The enhancement of engine performance to be attained by being able to vary the acceleration, velocity and travel time of the intake and exhaust valves in an engine is well known and appreciated in the art. However, the technology for providing a straight-forward, relatively inexpensive and highly reliable system has not been forthcoming. Increased use and reliance on micro electronic control systems for automotive vehicles and increased confidence in hydraulic as opposed to mechanical systems is now making substantial progress possible. In the area of intake and exhaust engine valves, prior development has been largely dependent upon sophisticated mechanical systems such as mechanically varying phase shift and other aspects of valve timing. Increased use of multiple valve engines has also been promoted.
The use or adoption of hydraulically controlled engine valves has been quite slow. Examples of known systems include those as shown in U.S. Pat Nos. 2,915,052; 3,240,191; 3,361,121; 3,534,718; 3,926,159; 3,963,006; and 4,200,067. In some instances, such as shown in U.S. Pat. No. 3,361,121 the poppet valve is maintained in a closed position by a mechanical coil spring, yet utilizes a hydraulic actuator to bias the valves in the open position. Several of the aforementioned patents also disclose the use of a rotary distributor valve to alternately couple the hydraulic actuator ports to a source of pressurized fluid, such as shown in U.S. Pat. Nos. 2,915,052 and 4,200,067. In certain of the aforementioned patents, it is also shown that the hydraulic fluid system is used to both open and close the engine valve, such feature being shown in U.S. Pat. Nos. 2,915,052 and 3,963,006.
However, none of the aforementioned systems provide a variable engine valve control system offering the simplicity, reliability, flexibility and efficiency believed necessary for use in the high production, high performance automotive engines being produced today and those that will be required in the near future.
In all its embodiments, the present invention includes a variable engine valve control system comprising a free moving valve with a piston attached to its top. The piston is subjected to fluid pressure acting on surfaces at both ends of the piston, with the surfaces being of unequal areas. The space at one end of the piston is connected to a source of high pressure fluid while the space at the other end can be connected either to a source of high pressure fluid or to a source of low pressure fluid, or disconnected from them both through action of controlling means such as solenoid valves.
Selective actuation and deactuation of the controlling means causes an inflow of pressurized fluid into a space at one end of said piston and an outflow of fluid from the space at the other end of the piston, such action leading to a change in the balance of forces acting on the piston and causing controlled motion of the valve from one fixed position to another.
The inflow of pressurized fluid is the result of fluid expansion from a pressurized container and the outflow of fluid leads to increased fluid compression in the pressurized container.
Moreover, the potential energy of pressurized fluid is converted into kinetic energy of the moving valve during acceleration, and the kinetic energy of the valve is converted back into potential energy of pressurized fluid during valve deceleration, thereby providing what can be referred to as a xe2x80x9cliquid spring.xe2x80x9d
Another feature of the system is the fact that the net fluid flow between the high pressure and low pressure source during operation is significantly less than the volume swept by the piston motion.
The timing of the valve opening and closing motions is controlled by varying the timing of the controlling means actuation. The stroke of the valve is determined by the duration of the controlling means actuation and the acceleration, velocity and travel time of the valve can be controlled by varying the pressure of the pressurized fluid.
The general system of the present invention as described above may be applied to an engine with more than two valves per cylinder and capable of activating selectively one or several intake (or exhaust) valves simultaneously.
It may also be applied to an engine with single intake and exhaust valves per cylinder where one pair of solenoids, for respectively controlling the transmission of high and low pressure fluid, may be used to control the intake/exhaust valves of a pair of cylinders 360xc2x0 off cycle.
In one form of the invention, the controlling means includes a rotary hydraulic distributor coupled with each solenoid valve, thereby permitting each solenoid valve to control operation of several free moving valves in succession.
Further, the present invention includes a system for assuring equal air delivery to all cylinders of an engine with a variable valve control employing actuators (such as the solenoid valves previously mentioned) controlled by electric pulses of variable duration and timing, the system including means for individually modifying the duration of the electric pulses controlling each individual actuator, and the modifications being of such nature as to assure that all actuators control the engine intake (or exhaust) valves in an identical manner.
In other words, the aforementioned technique assures that in all cylinders the valve stroke opening duration and resultant lift pattern will be identical.
More specifically, the system includes individually adjusted controlling means in all engine cylinders and a control system programmed to send variable electric control signals to each such controlling means. The control signals duration consists of the algebraic sum of a basic signal duration and a correction signal duration. The basic signal duration is determined by the control system as a function of engine operating conditions and is made equal for all engine intake valves and equal for all engine exhaust valves. The correction signal may be different for each of the controlling means and is supplied to the control system just before a given controlling means must be activated. A rotatable member is provided with tags attached to it, and each tag is taken from a specific controlling means and contains information on the correction signal required by the said specific controlling means. A sensor is installed in proximity of the rotatable member, and capable of reading the information contained in the tags and transmitting it elsewhere. The rotatable member rotates during engine operation with angular velocity preferably equal to half the crankshaft velocity on a four-stroke engine or equal to crankshaft velocity on a two stroke engine. The sensor reads the information on the individual tags successively passing the proximity of the sensor and transmits it to the control system. The location of the individual tags on the rotatable member is such that the information on each tag is read and sent to the control system just before the controlling means from which the tag was taken must be actuated.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.